Samples extracts (1l) were
analyzed by a Hewlett-Packard (HP) 6890GCsystem equipped with
a HP5973 mass selective detector and a DB-5 capillary column
(30mm×0.25mm×0.25m). Separation was achieved according
to the following program: the initial oven temperature was
80 ◦C (held time for 1 min), and increased to 275 ◦C at 15◦Cmin−1,
held for 1min; and then to 285 ◦C at 10◦Cmin−1, held for 1 min;
after that increased to 295 ◦C at 5◦Cmin−1, held for 1min. Nitrogen
was used as the carrier gas (1.5 ml min−1) and makeup gas
(35 ml min−1). A 1.0l aliquot of the extract was injected in the
splitless mode. The injector was held at 250 ◦C and the detector at
300 ◦C